Cardiovascular drugs: sequential nephron blockade: practice question

A Pharmacology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pharmacology · Cardiovascular drugs: sequential nephron blockade

Sample item

A man with cardiac oedema has a poor response to high-dose oral furosemide. Metolazone is added and he diureses briskly. Which electrolyte pattern is most characteristic of this combination?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Profound hypokalaemia with hyponatraemia

Furosemide blocks sodium reabsorption in the thick ascending limb, and metolazone blocks it in the distal tubule, a sequential nephron blockade that overcomes diuretic resistance. The extra sodium reaching the collecting duct drives potassium loss, and thiazide-like action adds hyponatraemia. Electrolytes and renal function need daily checking.

Option by option

  • A. Hyperkalaemia with metabolic acidosis

    Hyperkalaemia with acidosis suggests potassium-sparing diuretics, not loop plus thiazide-like drugs.

  • B. Hypernatraemia with hypercalcaemia

    Loop diuretics increase calcium loss and thiazide-like drugs only modestly raise serum calcium; hypernatraemia is not expected.

  • C. Profound hypokalaemia with hyponatraemia (correct)

    Correct. The combination produces marked potassium and sodium loss.

  • D. Hypermagnesaemia with hypocalcaemia

    Loop diuretics cause magnesium loss, and hypermagnesaemia is not expected.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, Profound hypokalaemia with hyponatraemia. Furosemide blocks sodium reabsorption in the thick ascending limb, and metolazone blocks it in the distal tubule, a sequential nephron blockade that overcomes diuretic resistance.

Why is "Hyperkalaemia with metabolic acidosis" not the answer?

Hyperkalaemia with acidosis suggests potassium-sparing diuretics, not loop plus thiazide-like drugs.

Why is "Hypernatraemia with hypercalcaemia" not the answer?

Loop diuretics increase calcium loss and thiazide-like drugs only modestly raise serum calcium; hypernatraemia is not expected.

Why is "Hypermagnesaemia with hypocalcaemia" not the answer?

Loop diuretics cause magnesium loss, and hypermagnesaemia is not expected.

What concept does this question test?

It tests Cardiovascular drugs: sequential nephron blockade in Pharmacology. The extra sodium reaching the collecting duct drives potassium loss, and thiazide-like action adds hyponatraemia. Electrolytes and renal function need daily checking.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Cardiovascular drugs: sequential nephron blockade?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.